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Run MongoDB with Custom Configuration

KubeDB supports providing custom configuration for MongoDB via PodTemplate. This tutorial will show you how to use KubeDB to run a MongoDB database with custom configuration using PodTemplate.

Before You Begin

At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using minikube.
Now, install KubeDB cli on your workstation and KubeDB operator in your cluster following the steps here.
To keep things isolated, this tutorial uses a separate namespace called demo throughout this tutorial.
```
$ kubectl create ns demo
namespace/demo created
```

Note: Yaml files used in this tutorial are stored in docs/examples/mongodb folder in GitHub repository kubedb/cli.

Overview

KubeDB allows providing a template for database pod through spec.podTemplate. KubeDB operator will pass the information provided in spec.podTemplate to the StatefulSet created for MongoDB database.

KubeDB accept following fields to set in spec.podTemplate:

metadata:
- annotations (pod’s annotation)
controller:
- annotations (statefulset’s annotation)
spec:
- args
- env
- resources
- initContainers
- imagePullSecrets
- nodeSelector
- affinity
- schedulerName
- tolerations
- priorityClassName
- priority
- securityContext

Read about the fields in details in PodTemplate concept,

CRD Configuration

Below is the YAML for the MongoDB created in this example. Here, spec.podTemplate.spec.env specifies environment variables and spec.podTemplate.spec.args provides extra arguments for MongoDB Docker Image.

In this tutorial, maxIncomingConnections is set to 100 (default, 65536) through args --maxConns=100.

apiVersion: kubedb.com/v1alpha1
kind: MongoDB
metadata:
  name: mgo-misc-config
  namespace: demo
spec:
  version: "3.6-v1"
  storageType: "Durable"
  storage:
    storageClassName: "standard"
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 50Mi
  podTemplate:
    spec:
      args:
      - --maxConns=100
      resources:
        requests:
          memory: "1Gi"
          cpu: "250m"
  terminationPolicy: Pause
  updateStrategy:
    type: RollingUpdate

$ kubedb create -f https://raw.githubusercontent.com/kubedb/cli/0.9.0/docs/examples/mongodb/configuration/mgo-misc-config.yaml
mongodb.kubedb.com/mgo-misc-config created

Now, wait a few minutes. KubeDB operator will create necessary PVC, statefulset, services, secret etc. If everything goes well, we will see that a pod with the name mgo-misc-config-0 has been created.

Check that the statefulset’s pod is running

$ kubectl get pod -n demo
NAME                READY     STATUS    RESTARTS   AGE
mgo-misc-config-0   1/1       Running   0          14m

Now, check if the database has started with the custom configuration we have provided.

Now, you can connect to this database through mongo-shell. In this tutorial, we are connecting to the MongoDB server from inside the pod.

$ kubectl get secrets -n demo mgo-misc-config-auth -o jsonpath='{.data.\user}' | base64 -d
root

$ kubectl get secrets -n demo mgo-misc-config-auth -o jsonpath='{.data.\password}' | base64 -d
TxDWYECTRXaWWueP

$ kubectl exec -it mgo-misc-config-0 -n demo sh

> mongo admin

> db.auth("root","TxDWYECTRXaWWueP")
1

> db._adminCommand( {getCmdLineOpts: 1})
{
	"argv" : [
		"mongod",
		"--dbpath=/data/db",
		"--auth",
		"--bind_ip=0.0.0.0",
		"--port=27017",
		"--maxConns=100"
	],
	"parsed" : {
		"net" : {
			"bindIp" : "0.0.0.0",
			"maxIncomingConnections" : 100,
			"port" : 27017
		},
		"security" : {
			"authorization" : "enabled"
		},
		"storage" : {
			"dbPath" : "/data/db"
		}
	},
	"ok" : 1
}

> exit
bye

You can see the maximum connection is set to 100 in parsed.net.maxIncomingConnections.

Snapshot Configuration

Snapshot also has the scope to be configured through spec.podTemplate. In this tutorial, an extra argument --gzip is passed to snapshot crd so that the output of mongodump is saved in gzip.

Below is the Snapshot CRD that is deployed in this tutorial. Create a secret mg-snap-secret from here for snapshot.

apiVersion: kubedb.com/v1alpha1
kind: Snapshot
metadata:
  name: snap-mgo-config
  namespace: demo
  labels:
    kubedb.com/kind: MongoDB
spec:
  databaseName: mgo-misc-config
  storageSecretName: mg-snap-secret
  gcs:
    bucket: kubedb
  podTemplate:
    spec:
      args:
      - --gzip

$ kubedb create -f https://raw.githubusercontent.com/kubedb/cli/0.9.0/docs/examples/mongodb/configuration/snapshot-misc-conf.yaml 
snapshot.kubedb.com/snap-mongodb-config created


$ kubedb get snap -n demo
NAME              DATABASENAME      STATUS      AGE
snap-mgo-config   mgo-misc-config   Succeeded   50m

Scheduled Backups

To configure BackupScheduler, add the require changes in PodTemplate just like snapshot object.

$ kubedb edit mg mgo-misc-config -n demo
apiVersion: kubedb.com/v1alpha1
kind: MongoDB
metadata:
  name: mgo-misc-config
  namespace: demo
  ...
spec:
  backupSchedule:
    cronExpression: '@every 1m'
    storageSecretName: mg-snap-secret
    gcs:
      bucket: kubedb
    podTemplate:
      spec:
        args:
        - --gzip
  ...
status:
  observedGeneration: 3$4212299729528774793
  phase: Running

$ kubedb get snap -n demo
NAME                              DATABASENAME      STATUS      AGE
mgo-misc-config-20181002-105247   mgo-misc-config   Succeeded   3m
mgo-misc-config-20181002-105349   mgo-misc-config   Succeeded   2m
mgo-misc-config-20181002-105449   mgo-misc-config   Succeeded   1m
mgo-misc-config-20181002-105549   mgo-misc-config   Succeeded   43s
snap-mongodb-config               mgo-misc-config   Succeeded   12m

Cleaning up

To cleanup the Kubernetes resources created by this tutorial, run:

kubectl patch -n demo mg/mgo-misc-config -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"
kubectl delete -n demo mg/mgo-misc-config

kubectl patch -n demo drmn/mgo-misc-config -p '{"spec":{"wipeOut":true}}' --type="merge"
kubectl delete -n demo drmn/mgo-misc-config

kubectl delete ns demo

If you would like to uninstall KubeDB operator, please follow the steps here.

Next Steps

Quickstart MongoDB with KubeDB Operator.
Snapshot and Restore process of MongoDB databases using KubeDB.
Take Scheduled Snapshot of MongoDB databases using KubeDB.
Initialize MongoDB with Script.
Initialize MongoDB with Snapshot.
Monitor your MongoDB database with KubeDB using out-of-the-box CoreOS Prometheus Operator.
Monitor your MongoDB database with KubeDB using out-of-the-box builtin-Prometheus.
Use private Docker registry to deploy MongoDB with KubeDB.
Use kubedb cli to manage databases like kubectl for Kubernetes.
Detail concepts of MongoDB object.
Detail concepts of Snapshot object.
Want to hack on KubeDB? Check our contribution guidelines.

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